1. Field of the Invention
The present invention relates to a motor with a plurality of pole teeth provided circumferentially adjacent to one another.
2. Related Background Art
FIG. 9 shows a motor including core assemblies 5, 6 and 7 that are placed overlapping in the axial direction to form a plurality of phases, wherein the core assemblies 5, 6 and 7 have coils 2, 3 and 4, respectively, that are wound generally cylindrically on a rotation shaft 1.
In the motor having such a structure, the core assemblies 5, 6 and 7 that form three phases are provided with pairs of disk-shaped grip sections 5a, 5a, 6a, 6a and 7a, 7a, respectively, that grip the coils 2, 3 and 4, respectively, in the axial direction. From the inner circumference end edge sections of the pairs of grip sections 5a, 5a, 6a, 6a and 7a, 7a extend pole teeth 5b1, 5b2, 6b1, 6b2, and 7b1, 7b2, respectively, that bend generally perpendicularly in the axial direction towards the counterpart in each grip section pair. The pole teeth 5b (5b1, 5b2), 6b (6b1, 6b2), and 7b (7b1, 7b2) are provided circumferentially adjacent to one another, as indicated in FIG. 10, for example.
However, in a motor having such a structure, of the core assemblies 5, 6 and 7 that form three phases described above, the pair of grip sections 6a and 6a of the center core assembly 6 provided in the center in the axial direction is provided as a separate body from one of the grip sections 5a and of the grip sections 7a of the end core assemblies 5 and 7, respectively, that are adjacent to the center core assembly 6. In other words, the grip sections 6a and 6a of the center core assembly 6 and one of the grip sections 5a and of the grip sections 7a of the end core assemblies 5 and 7, respectively, are each formed from different members. This is due to the fact that the winding direction of the coils 2, 3 and 4 is set in the same direction in every case, and to the fact that the performance of the motor, which is based on the relationship between the excitation order of the coils according to the winding specification and the rotation direction of the motor, requires that positions and a tooth width dimension of the pole teeth 5b1 and 6b1, as well as the pole teeth 6b2 and 7b1, that are each bent in a direction opposite to the adjacent core be formed in such a way that the pole teeth within each set overlap each other by generally one-half of a per unit rotation step (half step) in the axial direction, for example. As a result, the adjacent grip sections 6a and 5a, and the adjacent grip sections 6a and 7a, cannot be manufactured from a single member.
In conventional motors, the grip sections 6a and 6a of the center core assembly 6 and one of the grip sections 5a and of the grip sections 7a of the end core assemblies 5 and 7, respectively, adjacent to the center core assembly 6 are forced to have a structure that forms one set from two pieces, as shown in FIGS. 11 and 12; this has resulted in higher manufacturing cost for the core assemblies and a difficulty in achieving a motor that is thinner in the axial direction.